Classical monoclonal antibodies are currently produced in mammalian cells. Drawbacks of this method of production include the difficulty of producing and selecting appropriate clones, and the expense of culturing mammalian cells. The “next generation” of monoclonal antibodies are being engineered in E. coli. Recently, microbial expression of VH and VL domains tethered together by polypeptide linkers has created the capability of generating engineered “mini-antibodies.” These mini-bodies can be generated in E. coli in a virtually combinatorial fashion. These artificially created Fab or single chain Fv (scFv) can be linked together to form multimers, e.g., diabodies, triabodies and tetrabodies. Although they are capable of binding to antigens with almost antibody-like efficiency, these engineered, Fc deficient mini-antibodies lack the ability to interact with antigen presenting cells and are poorly immunogenic.
Existing solutions to the lack of immunogenicity of engineered antibodies involve directing one of the antigen binding sites to bind directly with immune cells. This brings them in apposition, but does not result in the same MHC class I priming as would be observed for a monoclonal antibody.